最近同学在把 springboot 升级到 2.x 版本的过程中碰到了小问题，可能升级变更里能找到信息，不过我们以学习为目的，可以看看代码是怎么样的
报错是在这段代码里的
org.apache.tomcat.util.http.fileupload.util.LimitedInputStream#checkLimit
private void checkLimit() throws IOException {
if (count > sizeMax) {
raiseError(sizeMax, count);
}
}
其中的 raiseError 是个抽象方法
protected abstract void raiseError(long pSizeMax, long pCount)
throws IOException;
具体的实现是在
public FileItemStreamImpl(FileItemIteratorImpl pFileItemIterator, String pName, String pFieldName, String pContentType, boolean pFormField, long pContentLength) throws FileUploadException, IOException {
this.fileItemIteratorImpl = pFileItemIterator;
this.name = pName;
this.fieldName = pFieldName;
this.contentType = pContentType;
this.formField = pFormField;
long fileSizeMax = this.fileItemIteratorImpl.getFileSizeMax();
if (fileSizeMax != -1L && pContentLength != -1L && pContentLength > fileSizeMax) {
FileSizeLimitExceededException e = new FileSizeLimitExceededException(String.format("The field %s exceeds its maximum permitted size of %s bytes.", this.fieldName, fileSizeMax), pContentLength, fileSizeMax);
e.setFileName(pName);
e.setFieldName(pFieldName);
throw new FileUploadIOException(e);
} else {
final MultipartStream.ItemInputStream itemStream = this.fileItemIteratorImpl.getMultiPartStream().newInputStream();
InputStream istream = itemStream;
if (fileSizeMax != -1L) {
istream = new LimitedInputStream(itemStream, fileSizeMax) {
protected void raiseError(long pSizeMax, long pCount) throws IOException {
itemStream.close(true);
FileSizeLimitExceededException e = new FileSizeLimitExceededException(String.format("The field %s exceeds its maximum permitted size of %s bytes.", FileItemStreamImpl.this.fieldName, pSizeMax), pCount, pSizeMax);
e.setFieldName(FileItemStreamImpl.this.fieldName);
e.setFileName(FileItemStreamImpl.this.name);
throw new FileUploadIOException(e);
}
};
}
this.stream = (InputStream)istream;
}
}
后面也会介绍到，这里我们其实主要是要找到这个 pSizeMax 是哪里来的
通过阅读代码会发现跟这个类 MultipartConfigElement 有关系
而在升级后的 springboot 中这个类已经有了自动装配类，也就是
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration
有了这个自动装配
@Configuration(
proxyBeanMethods = false
)
@ConditionalOnClass({Servlet.class, StandardServletMultipartResolver.class, MultipartConfigElement.class})
@ConditionalOnProperty(
prefix = "spring.servlet.multipart",
name = {"enabled"},
matchIfMissing = true
)
@ConditionalOnWebApplication(
type = Type.SERVLET
)
@EnableConfigurationProperties({MultipartProperties.class})
public class MultipartAutoConfiguration {
private final MultipartProperties multipartProperties;
public MultipartAutoConfiguration(MultipartProperties multipartProperties) {
this.multipartProperties = multipartProperties;
}
@Bean
@ConditionalOnMissingBean({MultipartConfigElement.class, CommonsMultipartResolver.class})
public MultipartConfigElement multipartConfigElement() {
return this.multipartProperties.createMultipartConfig();
}
而这个 MultipartProperties 类中
@ConfigurationProperties(
prefix = "spring.servlet.multipart",
ignoreUnknownFields = false
)
public class MultipartProperties {
private boolean enabled = true;
private String location;
private DataSize maxFileSize = DataSize.ofMegabytes(1L);
private DataSize maxRequestSize = DataSize.ofMegabytes(10L);
private DataSize fileSizeThreshold = DataSize.ofBytes(0L);
private boolean resolveLazily = false;
并且在前面 createMultipartConfig 中就使用了这个maxFileSize 的默认值
public MultipartConfigElement createMultipartConfig() {
MultipartConfigFactory factory = new MultipartConfigFactory();
PropertyMapper map = PropertyMapper.get().alwaysApplyingWhenNonNull();
map.from(this.fileSizeThreshold).to(factory::setFileSizeThreshold);
map.from(this.location).whenHasText().to(factory::setLocation);
map.from(this.maxRequestSize).to(factory::setMaxRequestSize);
map.from(this.maxFileSize).to(factory::setMaxFileSize);
return factory.createMultipartConfig();
}
而在 org.apache.catalina.connector.Request#parseParts 中，会判断 mce 的配置
private void parseParts(boolean explicit) {
ServletFileUpload upload = new ServletFileUpload();
upload.setFileItemFactory(factory);
upload.setFileSizeMax(mce.getMaxFileSize());
upload.setSizeMax(mce.getMaxRequestSize());
parts = new ArrayList<>();
try {
List<FileItem> items =
upload.parseRequest(new ServletRequestContext(this));
int maxPostSize = getConnector().getMaxPostSize();
int postSize = 0;
Charset charset = getCharset();
主要 org.apache.tomcat.util.http.fileupload.FileUploadBase#parseRequest
public List<FileItem> parseRequest(final RequestContext ctx)
throws FileUploadException {
final List<FileItem> items = new ArrayList<>();
boolean successful = false;
try {
final FileItemIterator iter = getItemIterator(ctx);
final FileItemFactory fileItemFactory = Objects.requireNonNull(getFileItemFactory(),
"No FileItemFactory has been set.");
final byte[] buffer = new byte[Streams.DEFAULT_BUFFER_SIZE];
while (iter.hasNext()) {
final FileItemStream item = iter.next();
final String fileName = item.getName();
final FileItem fileItem = fileItemFactory.createItem(item.getFieldName(), item.getContentType(),
item.isFormField(), fileName);
items.add(fileItem);
try {
Streams.copy(item.openStream(), fileItem.getOutputStream(), true, buffer);
} catch (final FileUploadIOException e) {
其中 org.apache.tomcat.util.http.fileupload.FileUploadBase#getItemIterator
public FileItemIterator getItemIterator(final RequestContext ctx)
throws FileUploadException, IOException {
try {
return new FileItemIteratorImpl(this, ctx);
} catch (final FileUploadIOException e) {
throw (FileUploadException) e.getCause();
}
}
这里就创建了 org.apache.tomcat.util.http.fileupload.impl.FileItemIteratorImpl
public FileItemIteratorImpl(final FileUploadBase fileUploadBase, final RequestContext requestContext)
throws FileUploadException, IOException {
this.fileUploadBase = fileUploadBase;
sizeMax = fileUploadBase.getSizeMax();
fileSizeMax = fileUploadBase.getFileSizeMax();
ctx = Objects.requireNonNull(requestContext, "requestContext");
skipPreamble = true;
findNextItem();
}
内部使用了前面给 upload 设置的文件大小上限 upload.setFileSizeMax(mce.getMaxFileSize());
然后在 findNextItem 里执行了初始化
private boolean findNextItem() throws FileUploadException, IOException {
if (eof) {
return false;
}
if (currentItem != null) {
currentItem.close();
currentItem = null;
}
final MultipartStream multi = getMultiPartStream();
for (;;) {
final boolean nextPart;
if (skipPreamble) {
nextPart = multi.skipPreamble();
} else {
nextPart = multi.readBoundary();
}
if (!nextPart) {
if (currentFieldName == null) {
eof = true;
return false;
}
multi.setBoundary(multiPartBoundary);
currentFieldName = null;
continue;
}
final FileItemHeaders headers = fileUploadBase.getParsedHeaders(multi.readHeaders());
if (currentFieldName == null) {
final String fieldName = fileUploadBase.getFieldName(headers);
if (fieldName != null) {
final String subContentType = headers.getHeader(FileUploadBase.CONTENT_TYPE);
if (subContentType != null
&& subContentType.toLowerCase(Locale.ENGLISH)
.startsWith(FileUploadBase.MULTIPART_MIXED)) {
currentFieldName = fieldName;
final byte[] subBoundary = fileUploadBase.getBoundary(subContentType);
multi.setBoundary(subBoundary);
skipPreamble = true;
continue;
}
final String fileName = fileUploadBase.getFileName(headers);
currentItem = new FileItemStreamImpl(this, fileName,
fieldName, headers.getHeader(FileUploadBase.CONTENT_TYPE),
fileName == null, getContentLength(headers));
currentItem.setHeaders(headers);
progressNotifier.noteItem();
itemValid = true;
return true;
}
} else {
final String fileName = fileUploadBase.getFileName(headers);
if (fileName != null) {
currentItem = new FileItemStreamImpl(this, fileName,
currentFieldName,
headers.getHeader(FileUploadBase.CONTENT_TYPE),
false, getContentLength(headers));
currentItem.setHeaders(headers);
progressNotifier.noteItem();
itemValid = true;
return true;
}
}
multi.discardBodyData();
}
}
这里面就会 new 这个 FileItemStreamImpl
currentItem = new FileItemStreamImpl(this, fileName,
fieldName, headers.getHeader(FileUploadBase.CONTENT_TYPE),
fileName == null, getContentLength(headers));
构造方法比较长
public FileItemStreamImpl(final FileItemIteratorImpl pFileItemIterator, final String pName, final String pFieldName,
final String pContentType, final boolean pFormField,
final long pContentLength) throws FileUploadException, IOException {
fileItemIteratorImpl = pFileItemIterator;
name = pName;
fieldName = pFieldName;
contentType = pContentType;
formField = pFormField;
final long fileSizeMax = fileItemIteratorImpl.getFileSizeMax();
if (fileSizeMax != -1 && pContentLength != -1
&& pContentLength > fileSizeMax) {
final FileSizeLimitExceededException e =
new FileSizeLimitExceededException(
String.format("The field %s exceeds its maximum permitted size of %s bytes.",
fieldName, Long.valueOf(fileSizeMax)),
pContentLength, fileSizeMax);
e.setFileName(pName);
e.setFieldName(pFieldName);
throw new FileUploadIOException(e);
}
final ItemInputStream itemStream = fileItemIteratorImpl.getMultiPartStream().newInputStream();
InputStream istream = itemStream;
if (fileSizeMax != -1) {
istream = new LimitedInputStream(istream, fileSizeMax) {
@Override
protected void raiseError(final long pSizeMax, final long pCount)
throws IOException {
itemStream.close(true);
final FileSizeLimitExceededException e =
new FileSizeLimitExceededException(
String.format("The field %s exceeds its maximum permitted size of %s bytes.",
fieldName, Long.valueOf(pSizeMax)),
pCount, pSizeMax);
e.setFieldName(fieldName);
e.setFileName(name);
throw new FileUploadIOException(e);
}
};
}
stream = istream;
}
当 fileSizeMax != 0 的时候就会初始化 LimitedInputStream，这就就是会在前面的
org.apache.tomcat.util.http.fileupload.FileUploadBase#parseRequest 中
Streams.copy(item.openStream(), fileItem.getOutputStream(), true, buffer);
这里的 item
final FileItemIterator iter = getItemIterator(ctx);
final FileItemFactory fileItemFactory = Objects.requireNonNull(getFileItemFactory(),
"No FileItemFactory has been set.");
final byte[] buffer = new byte[Streams.DEFAULT_BUFFER_SIZE];
while (iter.hasNext()) {
final FileItemStream item = iter.next();
调用了 FileItemIterator 迭代器的 next
@Override
public FileItemStream next() throws FileUploadException, IOException {
if (eof || (!itemValid && !hasNext())) {
throw new NoSuchElementException();
}
itemValid = false;
return currentItem;
}
这个 currentItem 就是前面 new 的 FileItemStreamImpl
然后在 Streams.copy 的时候调用 openStream 也就是 org.apache.tomcat.util.http.fileupload.impl.FileItemStreamImpl#openStream
@Override
public InputStream openStream() throws IOException {
if (((Closeable) stream).isClosed()) {
throw new FileItemStream.ItemSkippedException();
}
return stream;
}
这里的 stream 就是 FileItemStreamImpl 构造方法最后赋值的 stream，会在大小超过限制时抛出错误
而这个可以通过设置 properties 来修改，spring.servlet.multipart.max-file-size 和 spring.servlet.multipart.max-request-size
spring.servlet.multipart.max-file-size=100MB
spring.servlet.multipart.max-request-size=100MB
而老版本的 spring.http.multipart.maxFileSize
其实就是配置名称改了下，但是能看一下代码也是有点收获的。
